This invention relates to compositions comprising polyalkylenepolyamine derivatives which demonstrate improved properties as corrosion inhibitors when used in substantially aqueous media. This invention further concerns a method of making compositions of these water-soluble, polyalkylenepolyamine derivatives by reacting a hydrocarbon-soluble polyalkylenepolyamine composition with either an alkylating agent or an alkylene oxide. Additionally, this invention also relates to methods for using the polyalkylenepolyamine derivatives as effective corrosion inhibitors capable of protecting metal surfaces placed in contact with potentially corrosive chemicals.
Increasingly, industrial companies have begun to realize the economic importance of maintaining their equipment to ensure the longest operating life possible. This has been particularly true in the area of oil field operations.
As oil companies have been forced to go to new lengths in their search for oil, their operating equipment has also become more expensive and difficult to easily replace.
Given this level of investment, most companies have increasingly sought to rely on corrosion inhibitors to protect the metal surfaces on their drilling rigs and pipelines from the corrosive effects of the chemicals found in underground environments.
These corrosion inhibitors can either be applied directly to the potentially affected metal parts or injected into the oil well containing the corrosive chemicals. To achieve maximum effectiveness, the corrosion inhibitors should be dispersible or miscible in this underground medium.
Historically, alkylamines or polyamines have been the most commonly used corrosion inhibitors in oil well operations. A recent invention has also created compositions of polyalkylenepolyamines which are purported to possess even better corrosion inhibition properties. These chemical compositions are hydrocarbon-soluble, however, and experience in the field has shown that they are of limited effectiveness in the substantially aqueous environments one can potentially confront when drilling for oil. Since the base amines of these compositions are insoluble in an aqueous medium, they simply cannot work to maximum effectiveness as corrosion inhibitors in water-based environments.
The instant invention offers the ability to solve this limitation presently hampering these types of corrosion inhibitors. It proposes methods for the derivatization of polyalkylenepolyamine compositions into novel compositions of derivatized polyalkylenepolyamines.
These novel chemical compositions demonstrate increased water solubility, making them more effective in the heavily aqueous corrosive media, which are increasingly encountered in the ever-expanding search for new sources of oil.
In traditional oil production operations, the drilling rods are introduced into a subsurface environment largely consisting of hydrocarbon compounds. While some water is theoretically present in all wells, the corrosion and pitting which occur in these situations are largely the result of the effects of the hydrocarbon compounds on the rod. As noted previously, to achieve maximum effectiveness, a corrosion inhibitor should be dispersible in the medium in which it is to operate. Thus, the standard hydrocarbon-soluble amine or polyalkylenepolyamine composition provides adequate coverage in most "typical" oil production operations.
Increasingly, however, as our domestic supply of oil continues to dwindle, many oil companies are being forced to expand their quest for this valuable resource into many non-traditional areas. For example, a large percentage of the new wells being drilled are in substantially aqueous environments, presenting an even greater need to monitor the effects of corrosion on operating efficiency.
Numerous experiments have repeatedly demonstrated that the presence of water in underground environments greatly speeds up pitting and corrosion processes. Many new wells are affected by CO.sub.2 corrosion resulting from the carbonic acid which forms when CO.sub.2 comes in contact with water. Additionally, oxygen entering a heavily aqueous well also reacts with water in a manner that speeds up the effects of corrosion. Thus, it is especially vital to use effective corrosion inhibitors when operating in substantially aqueous media in order to counteract the added threat of corrosion in this type of environment.
Unfortunately, base amines and their more specialized polyalkylenepolyamine counterparts have not proven effective in these situations. Because most of these compounds are highly insoluble in water, when they are applied to drilling rods being used in substantially aqueous environments, they have shown a tendency to migrate from water, which is usually the layer in direct contact with the drilling rods, and dissolve in the hydrocarbon layer. With no protection between the dangerous aqueous layer and the drilling rod, corrosion proceeds relatively unabated.
Many in industry have attempted to solve this problem by searching for corrosion inhibitors which are dispersible in water, and thus effective in heavily aqueous media. The instant invention represents a successful culmination of one individual's efforts in this regard.
Numerous patents describe polyalkylenepolyamine compounds, their derivatives, and the processes for their production.
U.S. Pat. No. 4,314,083 discloses a process for selectively preparing non-cyclic polyalkylenepolyamine compounds by reacting an alkylenepolyamine compound with a hydroxy compound in the presence of a catalytically effective amount of salt, nitrogen, or sulfur-containing substance. This process is limited to short-chain alkyl groups consisting of no more than 4 carbon atoms.
U.S. Pat. No. 3,565,941 discloses a process for alkylating a polyalkylenepolyamine by first reacting the polyamine with an acid and then following with either an alkylating agent or a polyamine salt. This process is also specifically limited to hydrogen or short-chain alkyl groups of methyl or ethyl. The products also have limited uses as chemical intermediates, monomers, bases and flocculating agents.
Various other amine compounds have been recognized by the scientific community as effective in minimizing the corrosion of metal alloys. Prior patents disclose numerous quaternary, rosin and fatty amine compounds, as well as their corresponding derivatives, all of which are considered to be most beneficial in specific types of industrial operations. Alkylamines and polyamines are also accepted as particularly effective corrosion inhibitors in oil field operations. For years, however, researchers have been attempting to further refine these compounds in the hopes of developing other compositions which demonstrate even better corrosion inhibition properties.
U.S. Pat. No. 4,900,458, which is incorporated by reference in its entirety herein, represents a major success in this regard. Here, Schroeder et al. discovered methods for manufacturing novel polyalkylenepolyamine compositions in which an alkyl group of between 10-28 hydrocarbons was attached to the carbon atom instead of the nitrogen. This structural modification was shown to enable these hydrocarbon-soluble compositions to exhibit improved corrosion inhibition properties in oily media.
In contrast, the present invention provides excellent corrosion inhibitors useful in substantially aqueous media.